Re: Geeting hash_map values back

James Kanze <>
Tue, 22 Jan 2008 05:35:00 -0800 (PST)
On Jan 21, 3:07 pm, "C C++ C++" <> wrote:

Several comments...

I have thread create function like this
*)&ResultSet); // <--- ResultSet is hasp_map with around 10 key-values
in it.

Is "threadWork" a namespace or a class? The third argument to
pthread_create must be a pointer to an `extern "C"'
function---member functions (even static) can't be `extern "C"',
and there's really no point in putting an `extern "C"' in a

in member function is defined
void * threadWork::requestThread(void *ResultSet)
 cout << typeid(ResultSet).name() << ResultSet<<endl; // <<------ its
printing void * which is correct, how can i get my hash_map and its
values back ?

Use static_cast. With hash_map, there should be no problem. In
general, however, do be careful that you go through the right
types---something like:

    extern "C" void*
    threadFunction( void* p )
        Base* args = static_cast< Base* >( p ) ;
        // ...

    // ...

    Derived args ;
    pthread_create( ..., &args ) ;

has undefined behavior. (The call to pthread_create should be:
    pthread_create( ..., static_cast< Base* >( &args ) ) ;
And watch out for potential lifetime of object issues.)

James Kanze (GABI Software)
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